The present invention relates to trailers equipped with sliding axles, and more particularly to an alarm for indicating the status of a sliding axle system.
Many trailers are equipped with a system that enables the axles of the trailers to be moved relative to a load-bearing frame of the trailer. Such a system is often referred to as a “sliding axle” system. With this system, an operator can adjust the position of the axles relative to the trailer frame, and thereby alter the trailer's cornering ability, or redistribute a trailer load relative to the trailer axles and/or a truck to which the trailer is secured.
A sliding axle system typically includes an assembly secured to the suspension units, which are further secured to the axles of the trailer. The assembly slidingly engages the frame of the trailer or a track welded to the frame. Specifically, the assembly includes a set of pins, actuated by a handle, that retract from and extend into holes defined in the frame or track to lock the assembly in fixed position relative to the frame. In operation, an operator actuates the brakes of the sliding axle assembly, pulls the handle to extract the pins from the holes, thereby enabling the sliding axle assembly to slide relative to the frame and/or track. With the pins pulled, the operator drives the trailer forward or rearward using the tractor until the sliding axle assembly is in a desired position. After the assembly is moved, the handle is re-actuated to lock the pins in the holes and thereby secure the suspension unit in fixed relation to the trailer.
Some problems with sliding axle systems is that the pins may vibrate loose, or after adjustment, an operator may fail to properly lock the pins in the frame holes. Accordingly, as the trailer travels, the sliding axle assembly is free to move forward and rearward relative to the frame. This presents a dangerous situation if the trailer brakes are applied or if the trailer is pulled at excessive speeds.
One attempt to solve these problems is embodied in an electrical system which detects when the pins are not locked in the frame holes. U.S. Pat. No. 5,451,069 to Schueman discloses such a system, wherein an electrical microswitch illuminates a light when the locking pins are fully retracted and the air brakes are applied. Although this system provides a way to inform an operator that the sliding axle pins are not locked, it suffers a number of shortcomings. First, the electrical system must be coupled to the power supply or electrical system of the truck. This requirement takes a significant amount of time and care to ensure that the proper voltage is provided to the system. Second, the electrical switches of such an electrical system can easily short if not properly protected from the environment. Third, it is difficult for an operator to detect if the system is properly operating unless the operator inspects the pins.